The invention relates to semiconductor devices and, in particular, to semiconductor devices comprising a diode structure utilizing a Schottky barrier.
A semiconductor diode with a Schottky barrier between a metal and a semiconductor has a lower forward rising voltage than that of a device utilizing a PN junction. Also, its inverse direction restoring time is shorter, as it is free of an accumulation phenomenon caused by minority carriers. However, its inverse direction yield voltage is lower.
In an attempt to reduce the forward direction rising voltage in such a Schottky barrier semiconductor device, the metal of the Schottky barrier (hereinafter referred to as the barrier metal) has been varied, and the on-resistance has been reduced by decreasing the thickness of the epitaxial semiconductor layer contacted by the barrier metal. However, such techniques decrease the inverse direction yield voltage even more.
In other devices, disclosed, e.g., in Japanese Patent Document 59-35183 or in Japanese Patent Document 3-105975, regions of a p-type semiconductor in contact with the barrier metal are disposed at the surface of an n-type semiconductor contacted by the barrier metal, and depletion regions, extending into the n-type semiconductor layer from the adjoining p-type semiconductor regions when an inverse direction voltage is applied, are linked to each other to suppress leaking current flowing through the Schottky barrier. This results in a PN junction in parallel with the Schottky barrier, an in impaired switching characteristics due to injection of minority carriers from the PN junction.